Do you have any speakers or headphones plugged in while you are dong a recording? If you do, try removing them.
It may also help if you set both the Input Volume and Output Volume to the maximum levels when you are doing a recording. This should give you acceptable volume while you are recording and also make sure the recording itself gets good volume.
You can adjust these levels in System Preferences > Sound > Input. The Output Volume is your normal speaker volume, so make sure you turn it down when you are finished recording otherwise it will be super loud.
If nothing else helps I would then suggest doing a hard reinstall - uninstall Screen Recorder, reboot the machine, reinstall the latest update available on the site - https://www.jaksta.com/download/mac/jaksta-screen-recorder
From Liam @ 04 Sep 2019 11:09